An increasing number of abdominal surgical procedures are being performed with laparoscopic techniques in order to avoid a large skin incision. Typically in laparoscopic surgery, a special needle, similar to the pneumoneedles described in U.S. Pat. No. 4,808,168 to Warring and U.S. patent application No, 07/808,152 (both of which are herein expressly incorporated by reference), is inserted through the skin, and used to inflate the abdominal cavity with an insufflating gas such as CO.sub.2. Once the abdomen is adequately dilated, the needle is removed and a rigid access tube or cannula with a larger diameter (for example 10 or 11 mm) is passed through the skin in the same location.
The access tube provides access for laparoscopes or other laparoscopic surgical tools such as the stapler described in U.S. Pat. No. 5,040,715 or the surgical clip appliers described in U.S. Pat. Nos. 5,084,057 and 5,100,420. To drive the access tube through the skin, the surgeon places a trocar obturator in the lumen of the access tube to provide a sharp, leading edge for cutting tissue.
The art is replete with trocar devices such as those shown in U.S. Pat. Nos. 4,535,773, 4,601,710, 4,654,030, 4,902,280, and 4,931,042. A prior art trocar device typically comprises a sharp point for penetrating the skin, surrounded by a spring-loaded protective sleeve. As these trocar devices are urged through the skin, friction with the skin causes the protective sleeve to slide proximally (rearwardly). After the access tube has penetrated through the skin, there is no longer friction between the protective sleeve and the skin, and the spring is designed to urge the protective sleeve distally (forwardly) to cover the sharp point, locking the protective sleeve in position to reduce the risk of accidental puncture of the underlying organs.
Two typical "safety" trocars currently available are known as the "Auto Suture Surgiport" T.M. (generally available from U.S. Surgical of Norwalk, Conn.) and the "Endopath" T.M. (generally available from Ethicon of Somerville, N.J.). Trocars similar, but not identical to these are shown in U.S. Pat. No. 5,066,288 and 5,030,206. These types of prior art trocar devices are generally used during a surgical procedure and then disposed of after the surgical procedure is completed. Such prior art trocars tend to be expensive, particularly when a "safety" mechanism is included. Also, the presence of a "shield" necessarily reduces the size of the obturator/knife used with a given size of cannula and may cause other problems for the user or patient.
A more cost effective alternative to a disposable trocar is a completely reusable trocar, such as the Trocars generally available from Snowden-Pencer, Inc. of Tucker, Ga. or the Trocars generally available from Solos, Endoscopy, Inc. of Duluth Ga. A reusable trocar typically comprises an obturator assembly having sharp surfaces for cutting tissue, and a cannula or access tube assembly.
The obturator assembly of a typical reusable trocar may be used on a patient and then cleaned and sterilized for reuse on the same or a different patient. Reusable trocars tend to have minimal parts to afford quick and convenient cleaning and sterilization of the trocars.
Reusable trocars tend to encounter problems as the sharp tissue cutting surfaces of the obturator (including the tip) of a completely reusable trocar tend to become dull after even a few uses. Such "dulling" of the cutting surfaces of the trocar generally tends to increase the insertion force required to insert the trocar into the abdominal cavity.
Additionally, the sharp tissue cutting surfaces of a reusable trocar are vulnerable to mechanical damage from mishandling or other abuse during cleaning, sterilization and handling. For example, if the cutting surfaces or tip of a reusable trocar impulsively impact a solid object (such as when the obturator is inadvertently dropped on the floor or working area), the tip of the obturator tends to take a highly undesirable "hook" shape.
U.S. Pat. No. 4,601,710 discloses a trocar assembly having a trocar tip attached to the rest of the trocar assembly by set screws or threads. Also, AeSclepios Surgical Endoscopy, Inc. of Montreal, Quebec Canada and General Medical of Richmond Va. are believed to currently sell a reusable trocar having a trocar tip that is attached to the rest of the trocar assembly by threads.
Threading the trocar tip to the rest of the trocar assembly is believed to be undesirable because it may be difficult for the user to determine when the trocar tip is completely screwed into the rest of the trocar assembly. Although some surgeons prefer that the trocar tip slightly rotate relative to the cannula during insertion, some surgeons prefer that the trocar tip remain stationary relative to the cannula during insertion. If the trocar is used when the trocar tip is not completely screwed into the rest of the trocar assembly, the trocar tip may rotate relative to the rest of the trocar assembly and the cannula. Again, some surgeons wish to avoid such action. Also, the threaded portion of such a trocar is believed to be difficult to clean or sterilize as in some procedures, it may expose a healthcare worker to relatively sharp threaded surfaces that may be contaminated.
Additionally, using a set screw to attach the trocar tip to the rest of the trocar assembly is believed to be cumbersome or difficult for the user, as a user is required to manipulate a potentially fine set screw.